Here are a few pronunciation websites you might find useful. If you find any others, please email me and I will add them to this list.

Many Things.org

Pronuncian

Rachel's English Pronunciation Guide

Australian Network

University of Toronto Pronunciation Website

University of Iowa - Practicing Vowels

Rong Chang
How to pronounce specific vowels or consonants depending on the surrounding sounds: individual sounds in words
Okanagan College (scroll down to see the exercises)